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NASA NTRS2004

Survey of Software Assurance Techniques for Highly Reliable Systems

This document provides a survey of software assurance techniques for highly reliable systems including a discussion of relevant safety standards for various industries in the United States and Europe, as well as examples of methods used during software development projects. It contains one section for each industry surveyed: Aerospace, Defense, Nuclear Power, Medical Devices and Transportation. Each section provides an overview of applicable standards and examples of a mission or software development project, software assurance techniques used and reliability achieved.

Nelson, Stacy↗

NASA NTRS2004

Application of Thermo-Mechanical Measurements of Plastic Packages for Reliability Evaluation of PEMS

Thermo-mechanical analysis (TMA) is typically employed for measurements of the glass transition temperature (Tg) and coefficients of thermal expansion (CTE) in molding compounds used in plastic encapsulated microcircuits (PEMs). Application of TMA measurements directly to PEMs allows anomalies to be revealed in deformation of packages with temperature, and thus indicates possible reliability concerns related to thermo-mechanical integrity and stability of the devices. In this work, temperature dependencies of package deformation were measured in several types of PEMs that failed environmental stress testing including temperature cycling, highly accelerated stress testing (HAST) in humid environments, and bum-in (BI) testing. Comparison of thermo-mechanical characteristics of packages and molding compounds in the failed parts allowed for explanation of the observed failures. The results indicate that TMA of plastic packages might be used for quality evaluation of PEMs intended for high-reliability applications.

Sharma, Ashok K.↗

NASA NTRS1991

The Infeasibility of Experimental Quantification of Life-Critical Software Reliability

This paper affirms that quantification of life-critical software reliability is infeasible using statistical methods whether applied to standard software or fault-tolerant software. The key assumption of software fault tolerance|separately programmed versions fail independently|is shown to be problematic. This assumption cannot be justified by experimentation in the ultra-reliability region and subjective arguments in its favor are not sufficiently strong to justify it as an axiom. Also, the implications of the recent multi-version software experiments support this affirmation.

Butler, Ricky W.↗

NASA NTRS1997

Effect of Cyclic Thermal Loads on Fatigue Reliability in Polymer Matrix Composites

Technological solutions that will ensure the economic viability and environmental compatibility of a future High Speed Civil Transport plane are currently being sought. Lighter structural materials for both airframe primary structures and engine structure components are being investigated. We believe that such objectives can be achieved through the use of high-temperature composites as well as other conventional, lighter weight alloys. One of the prime issues for these structural components is assured long-term behavior with a specified reliability. An investigation was conducted to describe a computational simulation methodology for predicting fatigue life, reliability, and probabilistic long-term behavior of polymer matrix composites. A unified time-, stress-, and load-dependent Multi- Factor Interaction Equation (MFIE) model developed at the NASA Lewis Research Center was used to simulate the long-term behavior of polymer matrix composites.

Chamis, Christos C.↗

NASA NTRS2002

Low Temperature Reliability of Electronic Packages/Assemblies for Space Missions

A NASA-wide team, funded under the NASA Electronic Parts and Packaging Program (NEPP), was formed to collaborate and to establish reliability of various electronic parts/packaging and assemblies for operation under extreme cold temperatures. One of the primary objectives of the NEPP is to expedite the infusion of cutting edge technologies into the present and future NASA missions. Commercial-off-the-shelf (COTS) emerging electronic parts/packages due to their lower weight, increased functionality, and lower cost are excellent candidates for space missions if they are characterized to show that they will meet the stringent reliability and quality requirements. Characterizations, especially for the extreme cold temperatures, are required since very limited data are available by manufacturers or users. For severe military environments, the temperature conditions to -65 C are the lowest temperature for which these parts/packages and assemblies are qualified. New data beyond this relatively benign cold temperature are required for numerous NASA missions. Several parts/packages, based on the project recommendation for their immediate and future needs, were selected for detailed characterization to cold temperature regimes down to liquid nitrogen (-196 C), covering both Mars cold temperature (-125 C) and asteroid (- 180 C) lander environmental requirements. Numerous parts/packages and assemblies were characterized during extreme temperature environmental tests. Several electrical parameters were characterized at discrete temperatures to -185 C to determine if they remain within their specification ranges. Both packages and circuit boards were subjected to nondestructive testing including optical, X-ray, and acoustic microscopy to document their integrity prior to environment exposure. Package/board assemblies were also subjected to X-ray to characterize solder joint integrity including void levels. Both parts and assemblies were subjected to thermal cycling with a large temperature swing enveloping numerous NASA missions. Details of the performed tests and the results obtained are presented.

Patterson, Richard L.↗

NASA NTRS2003

A Step Made Toward Designing Microelectromechanical System (MEMS) Structures With High Reliability

The mechanical design of microelectromechanical systems-particularly for micropower generation applications-requires the ability to predict the strength capacity of load-carrying components over the service life of the device. These microdevices, which typically are made of brittle materials such as polysilicon, show wide scatter (stochastic behavior) in strength as well as a different average strength for different sized structures (size effect). These behaviors necessitate either costly and time-consuming trial-and-error designs or, more efficiently, the development of a probabilistic design methodology for MEMS. Over the years, the NASA Glenn Research Center s Life Prediction Branch has developed the CARES/Life probabilistic design methodology to predict the reliability of advanced ceramic components. In this study, done in collaboration with Johns Hopkins University, the ability of the CARES/Life code to predict the reliability of polysilicon microsized structures with stress concentrations is successfully demonstrated.

Nemeth, Noel N.↗

NASA NTRS2005

Reliability of Electronics for Cryogenic Space Applications Being Assessed

Many future NASA missions will require electronic parts and circuits that can operate reliably and efficiently in extreme temperature environments below typical device specification temperatures. These missions include the Mars Exploration Laboratory, the James Webb Space Telescope, the Europa Orbiter, surface rovers, and deep-space probes. In addition to NASA, the aerospace and commercial sectors require cryogenic electronics in applications that include advanced satellites, military hardware, medical instrumentation, magnetic levitation, superconducting energy management and distribution, particle confinement and acceleration, and arctic missions. Besides surviving hostile space environments, electronics capable of low-temperature operation would enhance circuit performance, improve system reliability, extend lifetime, and reduce development and launch costs. In addition, cryogenic electronics are expected to result in more efficient systems than those at room temperature.

Patterson, Richard L.↗

NASA NTRS2005

Reliability-Based Control Design for Uncertain Systems

This paper presents a robust control design methodology for systems with probabilistic parametric uncertainty. Control design is carried out by solving a reliability-based multi-objective optimization problem where the probability of violating design requirements is minimized. Simultaneously, failure domains are optimally enlarged to enable global improvements in the closed-loop performance. To enable an efficient numerical implementation, a hybrid approach for estimating reliability metrics is developed. This approach, which integrates deterministic sampling and asymptotic approximations, greatly reduces the numerical burden associated with complex probabilistic computations without compromising the accuracy of the results. Examples using output-feedback and full-state feedback with state estimation are used to demonstrate the ideas proposed.

Crespo, Luis G.↗

NASA NTRS2005

Sensor Data Distribution With Robustness and Reliability: Toward Distributed Components Model

In planetary surface exploration mission, sensor data distribution is required in many aspects, for example, in navigation, scheduling, planning, monitoring, diagnostics, and automation of the field tasks. The challenge is to distribute such data in the robust and reliable way so that we can minimize the errors caused by miscalculations, and misjudgments that based on the error data input in the mission. The ad-hoc wireless network on planetary surface is not constantly connected because of the nature of the rough terrain and lack of permanent establishments on the surface. There are some disconnected moments that the computation nodes will re-associate with different repeaters or access points until connections are reestablished. Such a nature requires our sensor data distribution software robust and reliable with ability to tolerant disconnected moments. This paper presents a distributed components model as a framework to accomplish such tasks. The software is written in Java and utilized the available Java Message Services schema and the Boss implementation. The results of field experimentations show that the model is very effective in completing the tasks.

Alena, Richard L.↗

NASA NTRS2005

On Space Exploration and Human Error: A Paper on Reliability and Safety

NASA space exploration should largely address a problem class in reliability and risk management stemming primarily from human error, system risk and multi-objective trade-off analysis, by conducting research into system complexity, risk characterization and modeling, and system reasoning. In general, in every mission we can distinguish risk in three possible ways: a) known-known, b) known-unknown, and c) unknown-unknown. It is probably almost certain that space exploration will partially experience similar known or unknown risks embedded in the Apollo missions, Shuttle or Station unless something alters how NASA will perceive and manage safety and reliability

Bell, David G.↗

NASA NTRS2005

Making a Reliable Actuator Faster and More Affordable

Before any rocket is allowed to fly and be used for a manned mission, it is first test-fired on a static test stand to verify its flight readiness. NASA s Stennis Space Center provides testing of Space Shuttle Main Engines, rocket propulsion systems, and related components with several test facilities. It has been NASA s test-launch site since 1961. The testing stations age with time and repeated use; and with aging comes maintenance; and with maintenance comes expense. NASA has been seeking ways to lower the cost of maintaining the stations, and has aided in the development of an improved reliable linear actuator that arrives onsite quickly and costs less money than other actuators. In general terms, a linear actuator is a servomechanism that supplies a measured amount of energy for the operation of another mechanical system. Accuracy, reliability, and speed of the actuator are critical to performance of the entire system, and these actuators are critical components of the engine test stands. Partnership An actuator was developed as part of a Dual-Use Cooperative Agreement between BAFCO, Inc., of Warminister, Pennsylvania, and Stennis. BAFCO identified four suppliers that manufactured actuator components that met the rigorous testing standards imposed by the Space Agency and then modified these components for application on the rocket test stands. In partnership with BAFCO, the existing commercial products size and weight were reworked, reducing cost and delivery time. Previously, these parts would cost between $20,000 and $22,000, but with the new process, they now run between $11,000 and $13,000, a substantial savings, considering NASA has already purchased over 120 of the units. Delivery time of the cost-saving actuators has also been cut from over 20 to 22 weeks to within 8 to 10 weeks. The redesigned actuator is commercially available, and the company is successfully supplying them to customers other than NASA.

Source record↗

NASA NTRS1997

The Interplay of Surface Mount Solder Joint Quality and Reliability of Low Volume SMAs

Spacecraft electronics including those used at the Jet Propulsion Laboratory (JPL), demand production of highly reliable assemblies. JPL has recently completed an extensive study, funded by NASA's code Q, of the interplay between manufacturing defects and reliability of ball grid array (BGA) and surface mount electronic components.

Spacecraft electronics electronic assemblies J-lea↗

NASA NTRS1994

The Development of a GaAs MMIC Reliability and Space Qualification Guide

NASA, JPL, and DOD are collaborating with GaAs MMIC users, manufacturers, and international space agencies to develop the “GaAs MMIC Reliability and Space Qualification Guide.” This paper discusses the need for a space qualification guide, provides a brief description of some common GaAs failure mechanisms, the approach that the NASA MMIC Reliability Assurance Program is following to develop the guide, and the status of the program.

exploration↗

NASA NTRS2002

Investigation of low glass transition temperature on COTS PEMs reliability

Many factors influence PEM component reliability.One of the factors that can affect PEM performance and reliability is the glass transition temperature (Tg) and the coefficient of thermal expansion (CTE) of the encapsulant or underfill. JPL/NASA is investigating how the Tg and CTE for PEMs affect device reliability under different temperature and aging conditions. Other issues with Tg are also being investigated. Some preliminary data will be presented on glass transition temperature test results conducted at JPL.

Glass transition temperature PEMs↗

NASA NTRS2006

An Approach to Reliability Testing of Microcircuits at Cryogenic Conditions

This viewgraph presentation reviews an approach to testing microcircuits at cryogenic temperatures. Standard testing procedures are not adequate to test microcircuits that are to operate at cryogenic temperatures. It is therefore necessary to perform analysis of operation conditions and reliability conditions for planning qualification testing of microcircuits at cryogenic temperatures. The major degradations for microcircuits operating at low temperatures depend on the number of switching cycles rather than on the duration of part operation. Therefore instead of accelerating degradation of the parts by increasing the level of stress, the possibility of which is very limited at cryogenic temperatures, the reliability testing can be based on the number of switching cycles.

Teverovsky, Alexander↗

NASA NTRS2007

Probabilistic Methods for Structural Reliability and Risk

A formal method is described to quantify structural reliability and risk in the presence of a multitude of uncertainties. The method is based on the materials behavior level where primitive variables with their respective scatters are used to describe that behavior. Computational simulation is then used to propagate those uncertainties to the structural scale where reliability and risk are usually specified. A sample case is described to illustrate the effectiveness, versatility, and maturity of the method. Typical results from this method demonstrate that the method is mature and that it can be used for future strategic projections and planning to assure better, cheaper, faster products for competitive advantages in world markets. The results also indicate that the methods are suitable for predicting remaining life in aging or deteriorating structures.

Chamis, Christos C.↗

NASA NTRS1990

Integrated circuit reliability testing

A technique is described for use in determining the reliability of microscopic conductors deposited on an uneven surface of an integrated circuit device. A wafer containing integrated circuit chips is formed with a test area having regions of different heights. At the time the conductors are formed on the chip areas of the wafer, an elongated serpentine assay conductor is deposited on the test area so the assay conductor extends over multiple steps between regions of different heights. Also, a first test conductor is deposited in the test area upon a uniform region of first height, and a second test conductor is deposited in the test area upon a uniform region of second height. The occurrence of high resistances at the steps between regions of different height is indicated by deriving the measured length of the serpentine conductor using the resistance measured between the ends of the serpentine conductor, and comparing that to the design length of the serpentine conductor. The percentage by which the measured length exceeds the design length, at which the integrated circuit will be discarded, depends on the required reliability of the integrated circuit.

Buehler, Martin G.↗

NASA NTRS2007

Reliability Effects of Surge Current Testing of Solid Tantalum Capacitors

Solid tantalum capacitors are widely used in space applications to filter low-frequency ripple currents in power supply circuits and stabilize DC voltages in the system. Tantalum capacitors manufactured per military specifications (MIL-PRF-55365) are established reliability components and have less than 0.001% of failures per 1000 hours (the failure rate is less than 10 FIT) for grades D or S, thus positioning these parts among electronic components with the highest reliability characteristics. Still, failures of tantalum capacitors do happen and when it occurs it might have catastrophic consequences for the system. This is due to a short-circuit failure mode, which might be damaging to a power supply, and also to the capability of tantalum capacitors with manganese cathodes to self-ignite when a failure occurs in low-impedance applications. During such a failure, a substantial amount of energy is released by exothermic reaction of the tantalum pellet with oxygen generated by the overheated manganese oxide cathode, resulting not only in destruction of the part, but also in damage of the board and surrounding components. A specific feature of tantalum capacitors, compared to ceramic parts, is a relatively large value of capacitance, which in contemporary low-size chip capacitors reaches dozens and hundreds of microfarads. This might result in so-called surge current or turn-on failures in the parts when the board is first powered up. Such a failure, which is considered as the most prevalent type of failures in tantalum capacitors [I], is due to fast changes of the voltage in the circuit, dV/dt, producing high surge current spikes, I(sub sp) = Cx(dV/dt), when current in the circuit is unrestricted. These spikes can reach hundreds of amperes and cause catastrophic failures in the system. The mechanism of surge current failures has not been understood completely yet, and different hypotheses were discussed in relevant literature. These include a sustained scintillation breakdown model [1-3]; electrical oscillations in circuits with a relatively high inductance [4-6]; local overheating of the cathode [5,7, 8]; mechanical damage to tantalum pentoxide dielectric caused by the impact of MnO2 crystals [2,9, 10]; or stress-induced-generation of electron traps caused by electromagnetic forces developed during current spikes [11]. A commonly accepted explanation of the surge current failures is that at unlimited current supply during surge current conditions, the self-healing mechanism in tantalum capacitors does not work, and what would be a minor scintillation spike if the current were limited, becomes a catastrophic failure of the part [l, 12]. However, our data show that the scintillation breakdown voltages are significantly greater that the surge current breakdown voltages, so it is still not clear why the part, which has no scintillations, would fail at the same voltage during surge current testing (SCT).

Teverovsky, Alexander↗